Risk factors of poor mid-term shoulder functional outcomes of osteosynthesis using antegrade intramedullary nailing for humeral shaft fractures: a retrospective study with a minimum 5-year follow-up.

BACKGROUND

Osteosynthesis using antegrade intramedullary nailing for humeral shaft fractures yields satisfactory bone union rates; however, it may adversely affect postoperative shoulder function. To date, factors affecting mid- or long-term shoulder functional outcomes following intramedullary nail fixation have not been clarified. In this study, we aimed to identify the risk factors for poor mid-term functional outcomes over 5 years postoperatively following antegrade intramedullary nail osteosynthesis for humeral shaft fractures.

METHODS

We retrospectively identified 33 patients who underwent surgery using an antegrade intramedullary nail for acute traumatic humeral shaft fractures and were followed up for at least 5 years postoperatively. We divided the patients into clinical failure and no clinical failure groups using an age- and sex-adjusted Constant score of 55 at the final follow-up as the cutoff value. We compared preoperative, perioperative, and postoperative factors between the two groups.

RESULTS

Five of the 33 patients had poor shoulder functional outcomes (adjusted Constant score < 55) at a mean follow-up of 7.5 years postoperatively. Proximal protrusion of the nail at the time of bone union (P = 0.004) and older age (P = 0.009) were significantly associated with clinical failure in the univariate analyses. Multivariate analysis showed that proximal protrusion of the nail (P = 0.031) was a risk factor for poor outcomes.

CONCLUSIONS

The findings of this study provide new information on predictive factors affecting mid-term outcomes following osteosynthesis using antegrade nails. Our results demonstrated that proximal protrusion of the nail was significantly associated with poor mid-term functional shoulder outcomes. Therefore, particularly in older adults, it is essential to place the proximal end of the intramedullary nail below the level of the articular cartilage.